The Room Simulator generates frequency responses for multiple sources at multiple locations in a rectangular room. It uses a frequency domain method based on the rigid boundary solution to the wave equation, modified for lossy boundaries. Results are equivalent to those obtained by the image source method in the time domain (Allen and Berkley 1978). Sources and listening positions can be altered by dragging on plan and elevation views of the room.
The Room Simulator window looks like this when first opened:
The left hand panel shows a view of the room with controls for room dimensions and the acoustic absorptions of the room's surfaces. The right hand side shows the frequency response at the main listening position and additional positions around it and has controls for which modal resonances are shown, the positions at which responses are to be calculated, the sources to be modelled and and how they are managed. The entire window can be resized and the divider between the left and right panels can be dragged to adjust the proportion allocated to each. The small triangles at the top of the divider allow either panel to be collapsed completely.
The dimensions and properties of the room are configured in the controls at the top of the room panel. The controls may be collapsed by clicking on the chevrons at the top right of the panel.
Dimensions may be displayed in metric or imperial units according to the selected Units. Regardless of the units selected, the dimension controls accept input in metric or imperial units, for example 2.5m, 250cm, 2500mm, 8.2ft, 8ft 2in, 8' 2", 8f2i, 8f2 and 98in are all valid entries. If an entry is a number without any units it is assumed to be in the selected measurement units.
If the room is well sealed select the Room is Sealed box, this increases the response boost at the lowest frequencies.
The surface absorptions define how sound is absorbed when it meets the surface. The absorptions are independent of angle or frequency. The higher the absorption figures, the more sound is absorbed at that surface and the more damped the room's modal resonances become.
Below the room panel controls are the views of the room, in plan and elevation.
The elevation view can be hidden by un-ticking the Show Elevation View box at the bottom of the panel. The main listening position is indicated by the head. Crosses around the head show the locations of any additional points selected for responses to be generated, in the image below the positions to left, right, in front and behind the main listening position have been selected.
A source can be selected by moving the mouse cursor over it. The source will be highlighted and can be moved by left-clicking and dragging or by using the arrow keys, the arrow keys allow finer adjustment of position. If the shift key is held down while dragging, movement will be restricted to either horizontal or vertical only. The source can be rotated by right-clicking or by pressing the R key (clockwise rotation) or L key (anticlockwise rotation). Note that rotating the source does not alter its response, all sources are treated as omnidirectional. The main listening position can similarly be moved using the mouse or, after highlighting it, the arrow keys, as can any of the additional listening positions. When a source or listening position is highlighted its location is shown:
When a source is highlighted the dimensions shown are to the acoustic centre, which is located at the centre of the front face. When a source is highlighted its individual contribution to the combined response at the main listening position is shown on the response graph.
The modal distribution for the room is shown on the response panel using lines that are colour-coded according to the axes they include:
The Modal Resonance Lines controls identify the colours of the individual lines and allow their transparency to be adjusted. Any lines which are not selected will not appear on the graph.
|Orange||Tangential Length, Width|
|Magenta||Tangential Length, Height|
|Cyan||Tangential Width, Height|
The Microphone Positions controls set the distances for the additional listening positions from the main position. They can also be adjusted by dragging the crosses on the room view.
The Speaker Controls allow a number of sources to be selected, including up to 4 subwoofers. The low frequency extension of each source can be configured independently - this is the frequency at which the source begins to roll off, it is not the bass management frequency, which is set using the Crossover Filter control. The room responses shown are the sums of the contributions of all the selected sources.
Subwoofers can be relocated to the corners or wall midpoints by pressing the appropriate buttons. If Show Anechoic Responses is selected the response plots remove the room contributions, leaving only the responses of the sources themselves. Sources can be time aligned at the main listening position and, if multiple subs are being simulated, the effect of time aligning each sub individually can be observed (note that if a symmetric placement of multiple subs is being used to minimise modal excitation the subs should not be individually aligned). The distances and times of flight to each source are shown and the effect of adding a time delay or gain adjustment to each source can be observed by altering the relevant controls.
Note that the simulation automatically level aligns sources to the main listening position, but that all the simulated subwoofers generate signals at the same level - this is necessary if they are arranged symmetrically to minimise modal excitation and reduce seat-to-seat variation.